Buffer for power looms



Oct. 24, 1961 F. G. REUTER ETAL 3,005,471

BUFFER FOR POWER LOOMS Filed Feb. 19, 1958 y 1 la. W

Claims priority, application Germany Feb. 21, 1957 6 Claims. (Cl. 139-166) This invention relates generally to power looms and, more particularly, to a buffer which checks the movement of the picker stick of a power loom.

It has been the practice heretofore to construct the buffer used to check the movement of a picker stick of a power loom from leather. Usually, the buffer has a hollow cylindrical shape formed by convolutely winding a leather sheet. The service life of such a buffer is relatively short because plastic deformation will take place as the buffer is hit by the picker stick. The deformed buffer no longer functions satisfactorily, so it is frequentlyv necessary to readjust the position of the buffer. Moreover, the flexibility of the leather decreases under impact by the picker stick requiring replacement of the buffer because the picker stick is stopped too abruptly by the relatively inflexible buffer.

It is therefore an object of this invention to provide a novel and improved buffer for a power loom. Still another object of the invention is to provide a buffer which will withstand the impact of the picker stick without substantial deformation and loss of flexibility. A still further object of the invention is to provide a power loom having a buffer of improved construction for checking the movement of the picker stick.

Other objects will become apparent from the following description with reference to the accompanying drawing in which:

FIGURE 1 is a side view of one embodiment of the invention;

FIGURE 2 is a top view of the embodiment of FIG- URE 1; and

FIGURE 3 is an elevation of a core provided for an embodiment of the invention.

In accordance with this invention, generally speaking, the foregoing objects and others are accomplished by providing a power loom with a buffer having a leather external surface for the picker stick to strike and having a core of elastic polyurethane foam. The buffer may be prepared by convolutely winding a leather sheet to form a hollow cylinder and inserting a core of elastic polyurethane foam in the cylinder. The polyurethane foam may be formed by any conventional process, but it is preferred to prepare it by reaction of water and a substantially linear hydroxyl terminated polyester or polyalkylene ether glycol and an organic polyisocyanate.

It has been found that the service life of the buffer provided by this invention is increased many times over that of the heretofore available hollow leather cylindrical buffers and that the impact of the picker stick is checked without excessive noise or deformation of the cylinder. The foam core exerts an outward pressure against the leather covering which avoids permanent deformation of the leather tube and makes it possible for the stroke of the picker stick to be checked at the same point each time it strikes the buffer.

In one embodiment of the invention, the convolutely Wound leather buffer having the polyurethane foam core has a supplementary layer of leather mounted on the striking surface thereof. This outer leather layer extends only about one-half way around the circumference of the bufier and it is this surface that is exposed to the picker stick. If the surface of the leather should become marred atent or deformed in anyway by the picker stick or otherwise, a new leather surface can be provided by merely replacing the leather which extends only half way round the cylinder.

As indicated hereinbefore, the core may be prepared from any elastic cellular polyurethane. Best results are obtained, however, when the polyurethane is formed by reaction of an organic diisocyanate with a substantially linear polyester having terminal hydroxyl groups. Such a polyester may be prepared by esterification of a dicarboxylic acid, such as, for example, adipic acid, succinic acid, terephthalic acid or the like, and a glycol, such as, for example, ethylene glycol, diethylene glycol, propylene glycol or the like. An excess of glycol is used to provide a polyester having terminal alcoholic hydroxyl groups instead of carboxyl groups. An excess of the organic diisocyanate is used in order that the resulting adduct has terminal NCO groups. Water is added to the reaction mixture to produce the pore structure by reaction of the water with NCO groups to form carbon dioxide which becomes entrapped in the viscous reaction liquid. Polyalkylene ether glycols prepared by thermal condensation of an alkylene oxide, such as, for example, ethylene oxide, propylene oxide, butylene oxide or the like, may be substituted for the polyester. In fact, any substantially linear organic compound having terminal hydroxyl groups and a molecular weight of at least about 500 may be used to prepare the polyurethane foam. Processes for preparing the foam are disclosed in US. Patent 2,764,565 and elsewhere and any of these processes can be used. Inasmuch as the invention is not concerned with the chemistry involved in the preparation of the polyurethane foam and is concerned only with the fabrication of a buffer having an elastic polyurethane foam core prepared by any of these heretofore available procedures, further discussion of the chemistry is not necessary. The polyurethane foam should have an elongation of from about 250 to about 350 for best results.

In one embodiment of the invention, the foam core is provided with discs at each end thereof formed from a substantially non-porous rubber-like polyurethane plastic of the type disclosed in U.S. Patents 2,729,618, 2,621,166 and 2,620,516. The polyurethane discs may be prepared by reaction of any organic compound having reactive hydrogen atoms with an organic diisocyanate and a cross-linker and casting the resulting polyurethane in accordance with the processes disclosed in these patents. It is not always necessary to provide the end disc to secure the core in place.

In some embodiments of the invention, and preferably in all of them, the foam core has a diameter somewhat greater than the internal diameter of the leather tube and is compressed in the tube. Any core diameter greater than the diameter of the cavity in the buffer is advantageous, but it is preferred that the core have a diameter of at least about 1.1 times the diameter of the cavity.

Referring now to the drawing for a more detailed description of the invention, FIGURES 1 and 2 illustrate a convolutely wound tubular body which may be formed by rolling or convolutely winding a leather strip or sheet. Bolt 2 extends through a perforation in the layers of leather forming the side walls of the tube and is to be used for fastening the buffer to a holder on the loom. The picker stick of a power loom is shown in a fragmentary view as 3. The surface of tube 1 exposed to picker stick 3 is covered with a layer of leather 4 which extends only about one-half way around the circumference of tube 1. This layer of leather 4 may be secured to tube 1 by any suitable means, such as, -for example, by means of rivet 5 having head 7. The various layers of tube 1 and layer 4 are perforated to receive rivet 5. A cylindrical elastic polyurethane foam core 8 having a diameter slightly larger than the internal diameter of tube 1 fills the cavity formed by the walls of tube 1. This core of polyurethane may be cut from a polyurethane plastic prepared in accordance with Example 1 of US. Patent 2,764,565. The foam used for the core has a bulk density of about 70 kg./m. and an elongation of at least about 250. Because the diameter of the foam core is greater than the internal diameter of the tube, it is compressed Within the tube and exerts a pressure against the wall, thereby preventing substantial deformation when the picker stick strikes the external surface. If necessary, any suitable adhesive, such as a polyurethane adhesive, may be used to secure the foam core within the tube.

The core shown in FIGURE 3 has an elastic polyurethane foam body 8 with substantially non-porous rubberlike polyurethane plastic ends 9. The disc-like members 9 are formed by casting a suitable polyurethane reaction mixture and curing it to form a solid rubber-like product. The discs maybe secured to the core with any suitable adhesive, such as, for example, a polyurethane adhesive. The polyurethane may be prepared in accordance with one of the examples of US. 2,729,618 or other patents referred to hereinbefore. Preferably, the diameter of the discs is greater than the diameter of the core and it may be substantially equal to the external diameter of the leather tube.

Although the invention has been described in considerable detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for this purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as is set forth in the claims.

What is claimed is:

l. A buffer for a power loom having a tubular leather body, a foam core compressed within the cavity of said tubular body and substantially non-porous polyurethane discs secured to each end of said core.

2. The buffer of claim 1 wherein said core has end discs of a diameter equal to the external diameter of the tubular body.

3. The buffer of claim 1 wherein the diameter of the core prior to insertion in the tube is greater than the internal diameter of the tube.

4. The buffer of claim 1 wherein said core has an elongation of from about 250 to about 350.

5. A bufier for a power loom comprising a cylindrical core of polyurethane foam, a convolutely wound leather tube surrounding said core, said core having a diameter in its unrestrained condition at least 1.1 times the inside diameter of said tube so that said core exerts an outward pressure on said tube when in the assembled position.

6. A buffer for a power loom to check the movement of a picker stick comprising a cylindrical core of polyurethane foam, a convolutely wound leather tube surrounding said core, an additional layer of leather covering at least the portion of the bufier struck by said picker stick, said additional layer being removably attached to said tube, said core having a diameter in its unrestrained condition at least 1.1 times the inside diameter of said tube so that said core exerts an outward pressure on said tube when in the assembled position.

References Cited in the file of this patent UNITED STATES PATENTS November 1954 (pp. 106-108 and 214-216). 

1. A BUFFER FOR A POWER LOOM HAVING A TUBULAR LEATHER BODY, A FOAM CORE COMPRESSED WITHIN THE CAVITY OF SAID TUBULAR BODY AND SUBSTANTIALLY NON-POROUS POLYURETHANE DISCS SECURED TO EACH END OF SAID CORE. 